Re: undotbs01.dbf just keeps growing

Jared,

It sure is nice to be missed. I'll make sure my secretary calls you about my future vacation plans...:)

You've nailed the problem. Autoextend, automatic undo and high undo retention is a recipe for high disk usage. The aum algorithm is such that preference is given to extending over reuse (especially since expire time propogation is a problem).

In order to find the length of the longest transaction, reference the v$undostat.maxquerylen value. Beware as there are known bugs with this view, so examine the output carefully to make sure it makes sense.

Daniel Fink

Jared Still wrote:

> The data file(s) for your undo tablespace is likely set
> as autoextend with an unlimited size.
>
> Run the attached script to check it.
>
> If so, you can use this to put a limit on it:
>
> alter database datafile '<your file name>' autoextend on next 200m
> maxsize 2000m;
>
> Adjust the numbers for your system.
>
> You should probably investigate why it continues to grow so large.
>
> I haven't yet converted our production databases to UNDO, having
> only recently migrated to 9i, so I don't have any useful advice
> past this.
>
> There are others that will be able to offer more for this. ( Dan
> Fink, where are you? This might even get Kirti to take a break
> from his book for a few minutes )
>
> HTH
>
> Jared

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Author: Daniel Fink
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